144 



ROLAND THAXTER ON THE 



infrequently in the species referred to, E. Grijlli, and in allied forms (fig. 83). It 

 should be noted that contraction of the spore contents from any cause might also produce 

 the same condition. In by far the majority of cases, the contents of the conidium, be- 

 ing more dense than that of the basidium, finally exert a greater pressure and forces the 

 columella back into the basidium, thus reversing its former position. The sum of these 

 opposing forces is very considerable, and as a natural result of their action a rupture of 

 the wall ensues at the point where they are opposed, that is, in a circle round the base 

 of the mother cell. This circle of rupture is usually very evident in discharged conidia, 

 being indicated by a slightly ragged projection which forms a ring at the base of the 

 papilla (fig. 85). As a result of this rupture, the conidium is discharged violently 

 into the air, often to a considerable distance. The columella commonly remains un- 

 broken by this discharge, although it is often greatly stretched and hangs from the ba- 

 sidium as a tongue-like projection. In other instances it may be accidentally broken 

 or this rupture may be normally connected with the discharge. In the latter case, a por- 

 tion of the protoplasm from the basidium is discharged with the spore and serves to 

 fix it to any object with which it may come in contact. 



The presence or absence of a columella in different species has been made a point of 

 structural difference to which more weight has, I think, been given than is justified by 

 the facts. The assumption that a columella exists and is wholly or partially destroyed 

 by the discharge of protoplasm above alluded to, in cases like E. muscae for example, 

 seems to me at least as warrantable as the apparently needless assumption of the absence 

 of so characteristic a structure. Moreover, the presence of a ruptured columella is often 

 indicated even in E. muscae by the numerous shreds that may be seen adhering to the 

 basidium after discharge (fig. 2). 



The conidia and their germination. — The conidia in their normal condition are of vari- 

 ous size and form, often varying considerably in the same species. The extremes of shape 

 are well represented by the nearly spherical spores of E. muscae and the slender tapering 

 form of E. gracilis. In size they vary from about 10/* in length to 75 p- or over. They 

 are usually hyaline, rarely slightly colored, with a fine granular contents; or, more com- 

 monly, contain coarsely granular protoplasm with large fat globules. In many instances, 

 these fatty bodies are so regular in size and shape that the conidia resemble asci filled with 

 spores ; a fact which probably accounts for the statement "Flocci fertiles intus sporidiis 

 globosis referti" in a description of what seems undoubtedly an Empusa, by Fries. 1 The 

 common occurrence, also, of very large single oil globules seems to have caused a similar 

 error. The walls of the conidium are, so far as known, always smooth, without spines 

 or similar modifications, and possess an adhesive quality which serves to attach them 

 readily to any object, even when their discharge is unaccompanied by the mass of pro- 

 toplasm above described. The basal portion of the spore is always more or less papil- 

 late, the papilla being in reality that portion of the spore proper which projects from 

 within the mother cell, from which it is distinguished by the ring of dehiscence. 



The conidium when discharged, if by chance it has come in contact with a suitable 

 host, adheres to it, and sends out a hypha of germination which enters its body as pre- 

 viously described. When placed in water the conidia give rise to one or more hyphae 



1 l. c. 



